In the fluid control apparatus used for semiconductor manufacturing equipment, integration has been progressing, which is made by such a manner that passage members of a plurality of fluid control devices butt against each other via a seal member and are coupled by means of bolts (e.g. Patent Literature 1).
In such a fluid control apparatus, in order to couple a pair of passage members, the passage members are, in most cases, coupled by means of four bolts that are placed in four corners of the passage members so as not to reach a fluid passage, whereby the seal member is securely fixed.